What are detectors used in radio and tv waves

In radio, a detector is a device or circuit that extracts information from a modulated radio frequency current or voltage. ... The transmitter was switched on and off to produce long or short periods of radio waves, spelling out text messages in Morse code. Radio waves are used for communication such as television and radio. Radio waves are transmitted easily through air. They do not cause damage if absorbed by the human body, and they can be reflected to change their direction. These properties make them ideal for communications.

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